This invention relates to lock and key sets, and more particularly, to a lock and key set including a tamper resistant, free-wheeling type lock assembly.
The purpose of a free-wheeling type lock is well known in the industry and various designs can be seen in the marketplace The construction of a free-wheeling type lock prevents the lock from being over-torqued during an attack by allowing the lock cylinder to de-clutch from the driving mechanism of the lock when an improper key, screwdriver or other device is used to turn the lock cylinder. To reset the lock, the cylinder is rotated back to a key-out position where the lock cylinder is again coupled to the driving mechanism. Although many concepts have been explored in the past, most free-wheeling locks have been costly and complicated to produce or have proven to be unreliable. Many designs are bulky in size or require multiple motions of the key, including various push in and turn sequences, to actuate their drive mechanisms.
Typically, free-wheeling type locks include a spring-loaded detent to achieve the clutching action between the moving parts of the lock. However, the use of a spring-actuated motion to move the internal mechanisms results in a non-positive motion that is subject to timing restraints.
To accommodate the multiple motion key sequences, known free-wheeling locks provide for axial displacement of the cylinder and/or the sleeve. The displacement is usually against the force of a spring bias to allow the cylinder and/or the sleeve to be returned to the key-out position when torque or axial motion on the key is released. However, the requirement for spring bias and additional motion can make the lock complicated to use.
The present invention provides a lock and key set including a free-wheeling lock assembly which is compact in size and requires few components. The lock assembly comprises a case, a lock barrel and a driver which is coupled to a latching mechanism which is operated by the free-wheeling lock assembly. The lock barrel is supported within the case for rotational and axial movement relative to the case. Tumblers of the lock assembly are operable between locking and releasing positions as a function of the presence and absence of a mating key in the key slot. In accordance with the free-wheeling aspect of the lock assembly, the lock barrel can be rotated relative to the case whether or not the mating key is present in the key slot.
Rotation of the lock barrel when the tumblers are in the releasing position causes the driver to rotate, operating the latching mechanism between the locked and unlocked conditions. However, the lock barrel is releaseably coupled to the driver so that when the tumblers are in the locking position, rotation of the lock barrel causes the lock barrel to become decoupled from the driver and rotation of the lock barrel is ineffective to cause the driver to operate the latching mechanism.
To this end, the lock assembly includes a translation mechanism which is coupled between the case and the lock barrel. The translation mechanism translates the lock barrel axially relative to the case in response to rotation of the lock barrel in the absence of the mating key in the key slot. This releases the coupling mechanism, permitting relative rotational movement between the lock barrel and the driver.
In one embodiment, the translation mechanism comprises first and second slidebars which are supported within the case for at least axial movement relative to the case. The tumblers cooperate with the slidebars to prevent relative axial movement between the slidebars and the lock barrel when the tumblers are in the locking position. However, the slidebars are movable axially relative to the lock barrel when the tumblers are in the releasing position.
When the tumblers are in the locking position, a portion of each tumbler extends into the corresponding mating notch in the first or second slidebar, preventing relative axial motion between the lock barrel and the slidebars. For this condition, if the barrel is rotated by some means, such as a screwdriver, the lock barrel will axially translate with respect to the case as the first and second slidebars follow the internal cam surfaces of the case causing the lock barrel to disengage from the driver. If a wrong key is present in the key slot and the lock barrel is rotated, all tumblers will not be in the releasing position and at least a portion of at least one tumbler extending into the mating notch in the first or second slidebar will cause the lock barrel to axially translate with respect to the case as the first and second slidebars are following the internal cam surfaces of the case, causing the lock barrel to disengage from the driver.
In accordance with another aspect of the invention, the axial translation of the lock barrel relative to the case results in preventing displacement of an actuator mechanism that is coupled to the latching mechanism. This prevents the latching mechanism from being operated during an attempt at compromising the lock assembly. In one embodiment, in which the coupling mechanism between the lock barrel and the latching mechanism includes a linearly movable actuator, a projection on the lock barrel engages the actuator to prevent linear movement of the actuator. In another embodiment, in which the coupling mechanism between the lock barrel and the latching mechanism includes a lever, a projection on the lock barrel engages the lever to prevent pivoting of the lever.